Gideon Yoffe (Israel)
yoffe @ mpia.de
Observations of Planet-Disk Interaction in the Inner Regions of Protoplanetary Disks with VLTI-MATISSE
Stars of mass ∼2M_⊙ are the most frequent hosts of giant planets. With about 15-20% of such stars hosting a giant planet, the search for disk progenitors of giant planets focuses on the long-lived disks around such stars - known as Herbig Ae stars. These disk-hosting pre-main sequence stars are empirically divided in two groups; GI and GII, based on their strong and weaker mid- to far-infrared excesses, respectively.
While this difference was initially attributed to a flared vs. a self-shadowed outer disk geometry, it was later found that the underlying cause for a GI-type SED is the presence of a very large (≥ 10 au) radial gap in the disk. In GII sources no evidence for such large gaps was found and they were thought to exhibit continuous disks.
However, higher resolution observations obtained with the first generation VLTI instrument MIDI, operating in the 8−13μm range, yielded indications for disk gaps being present on scales of ∼1 to a few au for a substantial fraction (∼1/3) of GII disks. Such gaps, considering the typical age of 5-10 Myr of these A-type stars, make plausible evidence of already-formed giant planets which have migrated to the inner disk and opened gaps and cavities.
Verifying this trend will be crucial in linking these disk populations to the observed trends in exoplanet studies, where giant planets seem to be mainly concentrated beyond 1 au in stars of mass >1.5M_⊙. Such links would inform giant planet formation theory - if gaps around few au are prevalent in both groups, the ideal condition for giant planets to form may have its origin in the commonalities of these groups (e.g., disk longevity) rather than any differences (e.g., flaring, disk size/mass) and direct the further theoretical efforts in the field. Here, the next generation VLTI mid-infrared Interferometer MATISSE, offering high spatial resolution observational capabilities, is needed to make the next qualitative leap forward: firmly establish the presence of gaps on these small scales as well as measure their size.
Supervisor: Thomas Henning (MPIA)